Data transmission and power control in a multihop relay communication system

ABSTRACT

Techniques for transmitting data with distributed and centralized scheduling in a multihop relay communication system are described. For distributed scheduling, a relay station may generate and send first channel quality information (CQI) to a base station and receive second CQI from a subscriber station. The relay station may receive data sent by the base station based on the first CQI and may resend the data to the subscriber station based on the second CQI. For centralized scheduling, the relay station may generate first CQI for the base station, receive second CQI from the subscriber station, and send both CQIs to the base station. The relay station may receive data sent by the base station based on the first CQI and may resend the data to the subscriber station based on a scheduling decision determined based on the second CQI. Techniques for distributed and centralized power control are also described.

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 12/042,901 to Dayal et. al. entitled “DATATRANSMISSION AND POWER CONTROL IN A MULTIHOP RELAY COMMUNICATION SYSTEM”filed Mar. 5, 2008; which claims priority to U.S. Provisional PatentApplication No. 60/895,388 to Dayal et. al. entitled “CHANNELINFORMATION MEASUREMENT AND REPORTING IN A WIRELESS MULTIHOP RELAYSYSTEM” filed Mar. 16, 2007; both of which are assigned to the assigneehereof and hereby expressly incorporated by reference herein.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to techniques for transmitting data in a wirelesscommunication system.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless systems may be multiple-access systemscapable of supporting multiple users by sharing the available systemresources. Examples of such multiple-access systems include CodeDivision Multiple Access (CDMA) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA)systems. Wireless systems have established themselves as a growing areain the field of telecommunications. The current trends and demands areto deliver multimedia services such as voice, video, interactive games,etc., with guaranteed Quality of Service (QoS). High data transmissioncapability is desirable in order to support high quality multimediaservices.

A wireless communication system may support multihop relay in order toimprove coverage and/or performance. With multihop relay, a base stationmay transmit data to a subscriber station via one or more relaystations. Each relay station may receive data from an upstream station(e.g., the base station or another relay station) and may retransmit thedata to a downstream station (e.g., the subscriber station or anotherrelay station). A transmission from one station to another station isconsidered as a hop. It may be desirable for each relay station toretransmit the data in an efficient manner.

SUMMARY

Techniques for transmitting data and performing power control in amultihop relay communication system are described herein. In one aspect,distributed scheduling and/or centralized scheduling may be supportedfor data transmission. In another aspect, distributed power controland/or centralized power control may be supported on the uplink.

In one design of distributed scheduling, a relay station may receive afirst pilot from a base station, estimate link quality for the basestation based on the first pilot, generate first channel qualityinformation (CQI) based on the estimated link quality, and send thefirst CQI to the base station. The relay station may also send a secondpilot to a subscriber station and receive second CQI generated by thesubscriber station based on the second pilot. The relay station mayreceive data sent by the base station based on the first CQI and mayresend the data to the subscriber station based on the second CQI.

In one design of centralized scheduling, a relay station may receive afirst pilot from a base station, estimate link quality for the basestation based on the first pilot, and generate first CQI based on theestimated link quality. The relay station may send a second pilot to asubscriber station and receive second CQI generated by the subscriberstation based on the second pilot. The relay station may send the firstCQI and the second CQI to the base station. The relay station mayreceive data sent by the base station based on the first CQI. The relaystation may also receive a scheduling decision determined by the basestation based on the second CQI. The relay station may resend the datato the subscriber station based on the scheduling decision.

In one design of distributed power control, a relay station may receivea first transmission (e.g., on a CQI channel) from a subscriber station,estimate link quality for the subscriber station based on the firsttransmission, generate a first power adjustment based on the estimatedlink quality, and send the first power adjustment to the subscriberstation. The relay station may send a second transmission (e.g., onanother CQI channel) to a base station and receive a second poweradjustment generated by the base station based on the secondtransmission. The relay station may receive data sent by the subscriberstation at transmit power determined based on the first poweradjustment. The relay station may resend the data to the base station attransmit power determined based on the second power adjustment.

In one design of centralized power control, a relay station may receivea first transmission from a subscriber station, estimate link qualityfor the subscriber station based on the first transmission, and send theestimated link quality for the subscriber station and a secondtransmission to a base station. The relay station may receive first andsecond power adjustments from the base station. The first poweradjustment may be generated based on the estimated link quality for thesubscriber station, and the second power adjustment may be generatedbased on the second transmission from the relay station. The relaystation may send the first power adjustment to the subscriber station.The relay station may receive data sent by the subscriber station attransmit power determined based on the first power adjustment. The relaystation may resend the data to the base station at transmit powerdetermined based on the second power adjustment.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system supporting multihop relay.

FIG. 2 shows a frame structure without multihop relay.

FIG. 3 shows a frame structure for multihop relay in a transparent mode.

FIG. 4 shows a frame structure for multihop relay in a non-transparentmode.

FIG. 5 shows a frame structure for three hops in the non-transparentmode.

FIG. 6 shows a scheme for distributed scheduling in 2-hop relay.

FIG. 7 shows a scheme for centralized scheduling in 2-hop relay.

FIG. 8 shows a process for supporting distributed scheduling.

FIG. 9 shows an apparatus supporting distributed scheduling.

FIG. 10 shows a process for supporting centralized scheduling.

FIG. 11 shows an apparatus supporting centralized scheduling.

FIG. 12 shows a scheme for distributed power control in 2-hop relay.

FIG. 13 shows a scheme for centralized power control in 2-hop relay.

FIG. 14 shows a process for supporting distributed power control.

FIG. 15 shows an apparatus supporting distributed power control.

FIG. 16 shows a process for supporting centralized power control.

FIG. 17 shows an apparatus supporting centralized power control.

FIG. 18 shows a block diagram of a base station, a relay station, and asubscriber station.

DETAILED DESCRIPTION

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA and SC-FDMAsystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such ascdma2000, Universal Terrestrial Radio Access (UTRA), etc. An OFDMAsystem may implement a radio technology such as Ultra Mobile Broadband(UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (which is also referred to asWi-Fi), IEEE 802.16 (which is also referred to as WiMAX), IEEE 802.20,Flash-OFDM®, etc. These various radio technologies and standards areknown in the art. The terms “radio technology”, “radio accesstechnology”, and “air interface” are often used interchangeably.

For clarity, certain aspects of the techniques are described below forWiMAX, which is covered in IEEE 802.16, entitled “Part 16: Air Interfacefor Fixed and Mobile Broadband Wireless Access Systems,” dated Oct. 1,2004, in IEEE 802.16e, entitled “Part 16: Air Interface for Fixed andMobile Broadband Wireless Access Systems Amendment 2: Physical andMedium Access Control Layers for Combined Fixed and Mobile Operation inLicensed Bands,” dated Feb. 28, 2006, and in IEEE 802.16j, entitled“Part 16: Air Interface for Fixed and Mobile Broadband Wireless AccessSystems Multihop Relay Specification,” dated Dec. 24, 2007. Thesedocuments are publicly available. The techniques may also be used forIEEE 802.16m, which is a new air interface being developed for WiMAX.IEEE 802.16j covers multihop relay and is intended to enhanceperformance of IEEE 802.16 standards by introducing relay stations. Someobjectives of IEEE 802.16j include extending coverage area, enhancingthroughput and system capacity, saving battery life of subscriberstations, and minimizing complexity of relay stations.

FIG. 1 shows a wireless communication system 100 that supports multihoprelay. For simplicity, FIG. 1 shows only one base stations (BS) 110,three relay stations (RS) 120, 122 and 124, and two subscriber stations(SS) 130 and 132. In general, a system may include any number of basestations and any number of relay stations that support communication forany number of subscriber stations. A base station is a station thatsupports communication for subscriber stations. A base station mayperform functions such as connectivity, management, and control of relaystations and subscriber stations. A base station may also be referred toas a Node B, an evolved Node B, an access point, etc. A relay station isa station that provides connectivity to other relay stations and/orsubscriber stations. A relay station may also provide management andcontrol of subordinate relay stations and/or subscriber stations. Theair interface between a relay station and a subscriber station may beidentical to the air interface between a base station and a subscriberstation. A base station may be coupled to a core network via a backhaul(not shown in FIG. 1) in order to support various services. A relaystation may or may not be directly coupled to the backhaul and may havelimited functionality to support multihop communication via that relaystation.

Subscriber stations may be dispersed throughout the system, and eachsubscriber station may be stationary or mobile. A subscriber station mayalso be referred to as a mobile station, a terminal, an access terminal,a user equipment, a subscriber unit, a station, etc. A subscriberstation may be a cellular phone, a personal digital assistant (PDA), awireless device, a wireless modem, a handheld device, a laptop computer,a cordless phone, etc. A subscriber station may communicate with a basestation and/or a relay station via the downlink (DL) and uplink (UL).The downlink (or forward link) refers to the communication link from thebase station or the relay station to the subscriber station. The uplink(or reverse link) refers to the communication link from the subscriberstation to the base station or the relay station.

In the example shown in FIG. 1, base station 110 may communicate withsubscriber station 130 via relay station 120. On the downlink, basestation 110 may transmit data for subscriber station 130 to relaystation 120, which may retransmit the data to subscriber station 130. Onthe uplink, subscriber station 130 may transmit data to relay station120, which may retransmit the data to base station 110. Base station 110and subscriber station 130 may also be able to communicate directly withone another.

Base station 110 may also communicate with subscriber station 132 viarelay stations 122 and 124. On the downlink, base station 110 maytransmit data for subscriber station 132 to relay station 122, which mayretransmit the data to relay station 124, which may further retransmitthe data to subscriber station 132. On the uplink, subscriber station132 may transmit data to relay station 124, which may retransmit thedata to relay station 122, which may further retransmit the data to basestation 110. Base station 110 may not be able to communicate directlywith subscriber station 132 and may rely on one or more relay stationsfor communication with subscriber station 132.

FIG. 1 shows an example of 2-hop communication between base station 110and subscriber station 130. FIG. 1 also shows an example of 3-hopcommunication between base station 110 and subscriber station 132. Ingeneral, a base station and a subscriber station may communicate via anynumber of hops. In the following description, from the perspective of agiven station, an upstream station is a station in an upstream path to abase station, and a downstream station is a station in a downstream pathto a subscriber station.

FIG. 2 shows an example frame structure 200 without multihop relay for atime division duplex (TDD) mode in IEEE 802.16. The transmissiontimeline may be partitioned into units of frames. Each frame may span apredetermined time duration, e.g., 5 milliseconds (ms), and may bepartitioned into a downlink subframe and an uplink subframe. Thedownlink and uplink subframes may be separated by a transmittransmission gap (TTG) and a receive transmission gap (RTG).

A number of physical subchannels may be defined. Each physicalsubchannel may include a set of subcarriers that may be contiguous ordistributed across the system bandwidth. A number of logical subchannelsmay also be defined and may be mapped to the physical subchannels basedon a known mapping. The logical subchannels may simplify the allocationof resources.

As shown in FIG. 2, a downlink subframe may include a preamble, a framecontrol header (FCH), a downlink map (DL-MAP), an uplink map (UL-MAP),and downlink (DL) bursts. The preamble may carry a known transmissionthat may be used by subscriber stations for frame detection andsynchronization. The FCH may carry parameters used to receive theDL-MAP, the UL-MAP, and the downlink bursts. The DL-MAP may carry aDL-MAP message, which may include information elements (IEs) for varioustypes of control information (e.g., resource allocation) for downlinkaccess. The UL-MAP may carry a UL-MAP message, which may include IEs forvarious types of control information for uplink access. The downlinkbursts may carry data for the subscriber stations being served. Anuplink subframe may include uplink bursts, which may carry data from thesubscriber stations scheduled for uplink transmission.

In general, the downlink and uplink subframes may cover any fraction ofa frame. In the example shown in FIG. 2, a frame includes 43 orthogonalfrequency division multiplexing (OFDM) symbols, the downlink subframeincludes 27 OFDM symbols, and the uplink subframe includes 16 OFDMsymbols. The frame, downlink subframe, and uplink subframe may also haveother durations.

As shown in FIG. 1, a base station may transmit data to a subscriberstation via one or more relay stations. The system may support atransparent mode and a non-transparent mode for multihop relay. Table 1lists some characteristics of the transparent mode and thenon-transparent mode, which are described in detail in theaforementioned IEEE 802.16j document.

TABLE 1 Mode Description Transparent Base station schedules transmissionon the downlink, mode generates assignment messages, and coordinatesretransmission by relay stations. Relay station retransmits datareceived from the base station but does not transmit preamble, FCH orMAP. Subscriber station receives assignment messages from the basestation and receives data from the relay station. Non- Base stationschedules transmission for the first hop transparent to the relaystation. mode Relay station can schedule retransmission for sub- sequenthop and generate assignment messages. Relay station retransmits datareceived from the base station and also transmits preamble, FCH and MAP.Subscriber station receives assignment messages and data from the relaystation.

FIG. 3 shows a frame structure for multihop relay in the transparentmode. The top half of FIG. 3 shows a frame 310 for a base station, andthe bottom half of FIG. 3 shows a frame 350 for a relay station.

Frame 310 includes a downlink subframe 320 and an uplink subframe 330.Downlink subframe 320 may be partitioned into a downlink access zone 322and an optional transparent zone 324. Each zone may include any numberof OFDM symbols. The base station may transmit a preamble, an FCH, aDL-MAP, a UL-MAP, a relay MAP (R-MAP), and downlink bursts to the relaystation and/or subscriber stations in downlink access zone 322. TheR-MAP may carry an R-MAP message that may convey the detailed allocationfor the relay station in optional transparent zone 324. The base stationmay or may not transmit during zone 324. Uplink subframe 330 may bepartitioned into an uplink access zone 332 and an uplink relay zone 334.Uplink access zone 332 may include uplink bursts sent by subscriberstations to the base station and/or the relay station. Uplink relay zone334 may include uplink bursts sent by the relay station to the basestation.

Frame 350 includes a downlink subframe 360 and an uplink subframe 370.Downlink subframe 360 may be partitioned into a downlink access zone 362and an optional transparent zone 364, which may be time-aligned withzones 322 and 324 of frame 310. Zones 362 and 364 are separated by arelay receive transition gap (R-RTG). The relay station may receive thepreamble, FCH, DL-MAP, UL-MAP, R-MAP, and downlink bursts from the basestation in downlink access zone 362. The relay station may retransmitsome or all of the data received from the base station in optionaltransparent zone 364 as indicated by the R-MAP message. Uplink subframe370 may be partitioned into an uplink access zone 372 and an uplinkrelay zone 374, which may be time-aligned with zones 332 and 334 offrame 310. Uplink access zone 372 may include uplink bursts sent bysubscriber stations to the base station and/or the relay station. Uplinkrelay zone 374 may include uplink bursts sent by the relay station tothe base station.

In the transparent mode, the base station may send a DL-MAP message thatconveys the downlink burst assigned to each subscriber station beingserved. A subscriber station may receive the preamble, FCH, and DL-MAPmessage from the base station and may determine its assigned downlinkburst based on the DL-MAP message. The subscriber station may thenprocess the assigned downlink burst, which may be transmitted by eitherthe base station or the relay station. The relay station may receivedata from the base station and retransmit the data as indicated by thebase station.

FIG. 4 shows a frame structure for multihop relay in the non-transparentmode. The top half of FIG. 4 shows a frame 410 for a base station, andthe bottom half of FIG. 4 shows a frame 450 for a relay station.

Frame 410 includes a downlink subframe 420 and an uplink subframe 430.Downlink subframe 420 may be partitioned into a downlink access zone 422and a downlink relay zone 424. The base station may transmit a preamble,an FCH, a DL-MAP, a UL-MAP, and downlink bursts in downlink access zone422 to subscriber stations. The base station may transmit a relay FCH(R-FCH), an R-MAP, and downlink bursts in downlink relay zone 424 to therelay station. Uplink subframe 430 may be partitioned into an uplinkaccess zone 432 and an uplink relay zone 434. Uplink access zone 432 mayinclude uplink bursts sent by subscriber stations to the base stationand/or the relay station. Uplink relay zone 434 may include uplinkbursts sent by the relay station to the base station.

Frame 450 includes a downlink subframe 460 and an uplink subframe 470.Downlink subframe 460 may be partitioned into a downlink access zone 462and a downlink relay zone 464, which may be time-aligned with zones 422and 424 of frame 410. The relay station may receive the R-FCH, R-MAP,and downlink bursts from the base station in downlink relay zone 464.The relay station may transmit a preamble, an FCH, a DL-MAP, a UL-MAP,and downlink bursts for some or all of the data received from the basestation in downlink access zone 462 of the next frame. There is a delayof one frame for the data retransmitted by the relay station. Uplinksubframe 470 may be partitioned into an uplink access zone 472 and anuplink relay zone 474, which may be time-aligned with zones 432 and 434of frame 410. Uplink access zone 472 may include uplink bursts sent bysubscriber stations to the base station and/or the relay station. Uplinkrelay zone 474 may include uplink bursts sent by the relay station tothe base station.

In the non-transparent mode, the base station may send an R-MAP messagethat may convey the downlink bursts for each relay station in downlinkrelay zone 424. A relay station may receive the data from the basestation as indicated by the R-MAP message. The relay station maytransmit a preamble, an FCH, a DL-MAP, a UL-MAP, and downlink burstscontaining the data received from the base station in downlink accesszone 462 to subscriber stations. The DL-MAP message may convey thedownlink burst assigned by the relay station to each subscriber station.Each subscriber station may receive the preamble, FCH, DL-MAP message,and data from the relay station and may not need to receive anythingfrom the base station.

FIG. 5 shows a frame structure for three hops in the non-transparentmode. The top of FIG. 5 shows a frame 510 for a base station, the middleof FIG. 5 shows a frame 530 for a first relay station (RS1), and thebottom of FIG. 5 shows a frame 550 for a second relay station (RS2).

For frame 510, the downlink subframe may be partitioned into a downlinkaccess zone 512 and a downlink relay zone 516. The uplink subframe maybe partitioned into an uplink access zone 522 and an uplink relay zone526. The base station may transmit to subscriber stations in downlinkaccess zone 512, transmit to the first relay station in downlink relayzone 516, receive from subscriber stations in uplink access zone 522,and receive from the first relay station in uplink relay zone 526.

For frame 530, the downlink subframe may be partitioned into a downlinkaccess zone 532 and downlink relay zones 534 and 536. The uplinksubframe may be partitioned into an uplink access zone 542 and uplinkrelay zones 544 and 546. The first relay station may receive from thebase station in downlink relay zone 536, transmit to subscriber stationsin downlink access zone 532, and transmit to the second relay station indownlink relay zone 534. The first relay station may receive fromsubscriber stations in uplink access zone 542, receive from the secondrelay station in uplink relay zone 544, and transmit to the base stationin uplink relay zone 546.

For frame 550, the downlink subframe may be partitioned into a downlinkaccess zone 552 and downlink relay zones 554 and 556. The uplinksubframe may be partitioned into an uplink access zone 562 and uplinkrelay zones 564 and 566. The second relay station may receive from thefirst relay station in downlink relay zone 554 and transmit tosubscriber stations in downlink access zone 552 and downlink relay zone556. The second relay station may receive from subscriber stations inuplink access zone 562 and uplink relay zone 566 and transmit to thefirst relay station in uplink relay zone 564. Relay zones 556 and 566may also be omitted.

FIGS. 3 and 4 show two frame structures that support two hops via onerelay station. FIG. 5 shows a frame structure that supports three hopsvia two relay stations. For the frame structures in FIGS. 4 and 5, thereis a delay of one frame for the data retransmitted by each relaystation. Other frame structures may also be used for multihop relay. Ingeneral, a frame may include any number of zones for basestation-subscriber station (BS-SS) communication, relay station-relaystation (RS-RS) communication, and relay station-subscriber station(RS-SS) communication.

In an aspect, the system may support distributed scheduling and/orcentralized scheduling for data transmission on the downlink withmultihop relay. In one design, both distributed and centralizedscheduling may be used for the non-transparent mode, and onlycentralized scheduling is used for the transparent mode. Table 2 listssome characteristics of distributed and centralized scheduling.

TABLE 2 Scheduling Description Distributed Base station transmits datato relay station based on scheduling CQI received from the relaystation. Relay station retransmits the data to subscriber station basedon CQI received from the subscriber station. Centralized Base stationreceives CQI from relay station and CQI scheduling from subscriberstation and schedules transmission on both BS-RS link and RS-SS link.Relay station retransmits data to subscriber station based on schedulingdecision from the base station for the RS-SS link.

FIG. 6 shows a scheme for transmitting data with distributed schedulingfor 2-hop relay. The first hop is from base station 110 to relay station120, and the second hop is from relay station 120 to subscriber station130.

For the first hop, base station 110 may transmit pilot to relay station120. Relay station 120 may estimate the quality of the BS-RS link basedon the pilot from base station 110, generate CQI indicative of the BS-RSlink quality (which is denoted as CQI #1), and send CQI #1 to basestation 110. CQI may be provided in the form of acarrier-to-interference-and-noise ratio (CINR) report or some otherformat. Base station 110 may schedule BS-RS transmission for relaystation 120 based on CQI #1. For example, base station 110 may allocateradio resources to relay station 120 and/or select a modulation andcoding scheme for the BS-RS transmission based on CQI #1. Base station110 may send data for subscriber station 130 to relay station 120 asscheduled based on CQI #1.

For the second hop, relay station 120 may transmit pilot to subscriberstation 130. Subscriber station 130 may estimate the quality of theRS-SS link based on the pilot from relay station 120, generate CQIindicative of the RS-SS link quality (which is denoted as CQI #2), andsend CQI #2 to relay station 120. Relay station 120 may schedule RS-SStransmission for subscriber station 130 based on CQI #2 and may resendthe data received from base station 110 to subscriber station 130 asscheduled based on CQI #2.

Relay station 120 may periodically send CQI #1 on a CQI channel (CQICH)to base station 110, and subscriber station 130 may periodically sendCQI #2 on another CQICH to relay station 120. Base station 110 mayallocate the CQICH for relay station 120, and relay station 120 mayallocate the CQICH for subscriber station 130. The CQICH allocation foreach link may be provided via (i) a FAST-FEEDBACK Allocation IE thatindicates a region used for CQI, which may be partitioned into slots,and (ii) a CQICH Allocation IE that indicates which slot is allocated toeach station as well as how often and/or when each station should sendCQI.

FIG. 7 shows a scheme for transmitting data with centralized schedulingfor 2-hop relay. Base station 110 may transmit pilot to relay station120, and relay station 120 may transmit pilot to subscriber station 130.Relay station 120 may estimate the quality of the BS-RS link based onthe pilot from base station 110 and generate CQI #1 indicative of theBS-RS link quality. Similarly, subscriber station 130 may estimate thequality of the RS-SS link based on the pilot from relay station 120,generate CQI #2 indicative of the RS-SS link quality, and send CQI #2 torelay station 120. Relay station 120 may send CQI #1 generated by therelay station as well as CQI #2 received from subscriber station 130 tobase station 110.

Base station 110 may schedule BS-RS transmission for relay station 120based on CQI #1 and may also schedule RS-SS transmission for subscriberstation 130 based on CQI #2. Base station 110 may send data forsubscriber station 130 to relay station 120 as scheduled based on CQI#1. Base station 110 may also send a scheduling decision for the RS-SStransmission to relay station 120. Relay station 120 may receive thedata and scheduling decision from base station 110 and may resend thedata to subscriber station 130 as indicated by the scheduling decision.

FIGS. 6 and 7 show distributed and centralized scheduling, respectively,for 2-hop relay. Distributed and centralized scheduling for more thantwo hops may be performed in similar manner.

For N-hop distributed scheduling, where N may be any integer value, arelay station may receive pilot from the next upstream station, whichmay be a base station or another relay station. The relay station maygenerate CQI for the next upstream station based on the received pilotand may send the CQI to this upstream station. The relay station mayreceive data sent by the next upstream station based on the CQI sent bythe relay station. The relay station may also send pilot to the nextdownstream station, which may be a subscriber station or another relaystation. The relay station may receive CQI generated by the nextdownstream station based on the pilot from the relay station. The relaystation may resend the data received from the next upstream station tothe next downstream station based on the CQI received from thisdownstream station.

For N-hop centralized scheduling, a relay station may receive CQI fromeach downstream station. The relay station may also generate CQI for thenext upstream station. The relay station may send the CQI generated forthe next upstream station as well as CQIs from all downstream stationsto the next upstream station. The relay station may receive data sent bythe next upstream station based on the CQI generated by the relaystation. The relay station may also receive (i) a scheduling decisionfor the relay station, which may be generated by a base station based onthe CQI from the next downstream station, and (ii) scheduling decisionsfor other downstream relay stations, if any, which may be generated bythe base station based on the CQIs from their downstream stations. Therelay station may resend the data to the next downstream station basedon the scheduling decision for the relay station. The relay station mayalso send the scheduling decisions for other downstream relay stations,if any, to the next downstream station.

FIG. 8 shows a design of a process 800 performed by a relay station fordistributed scheduling in multihop relay, which may correspond to FIG.6. The relay station may receive a first transmission from a firststation, which may be a base station or another relay station (block812). The first transmission may comprise pilot, control information,etc. The relay station may estimate link quality for the first stationbased on the first transmission (block 814), generate first CQI based onthe estimated link quality for the first station (block 816), and sendthe first CQI to the first station (block 818). The relay station mayalso send a second transmission to a second station, which may be asubscriber station or another relay station (block 820). The secondtransmission may comprise pilot, control information, etc. The relaystation may receive second CQI generated by the second station based onthe second transmission (block 822). The relay station may receive datasent by the first station based on the first CQI (block 824) and mayresend the data to the second station based on the second CQI (block826).

The first station may schedule data transmission from the first stationto the relay station based on the first CQI. The relay station mayschedule data transmission from the relay station to the second stationbased on the second CQI. The scheduling by each station may includeassigning radio resources for data transmission, selecting a modulationand coding scheme for the data transmission, etc.

FIG. 9 shows a design of an apparatus 900 for supporting distributedscheduling in multihop relay. Apparatus 900 includes a module 912 toreceive a first transmission (e.g., pilot) from a first station, amodule 914 to estimate link quality for the first station based on thefirst transmission, a module 916 to generate first CQI based on theestimated link quality for the first station, a module 918 to send thefirst CQI to the first station, a module 920 to send a secondtransmission (e.g., pilot) to a second station, a module 922 to receivesecond CQI generated by the second station based on the secondtransmission, a module 924 to receive data sent by the first stationbased on the first CQI, and a module 926 to resend the data to thesecond station based on the second CQI.

FIG. 10 shows a design of a process 1000 performed by a relay stationfor centralized scheduling in multihop relay, which may correspond toFIG. 7. The relay station may receive a first transmission from a firststation, which may be a base station or another relay station (block1012). The first transmission may comprise pilot, control information,etc. The relay station may estimate link quality for the first stationbased on the first transmission (block 1014), and generate first CQIbased on the estimated link quality for the first station (block 1016).The relay station may send a second transmission to a second station,which may be a subscriber station or another relay station (block 1018).The second transmission may comprise pilot, control information, etc.The relay station may receive second CQI generated by the second stationbased on the second transmission (block 1020).

The relay station may send the first CQI and the second CQI to the firststation (block 1022). The relay station may send the second CQI on theCQICH with the first CQI, on another feedback channel, in a MediumAccess Control (MAC) management message, or via some other means to thefirst station. The relay station may receive data sent by the firststation based on the first CQI (block 1024). The relay station may alsoreceive a scheduling decision determined by a base station based on thesecond CQI (block 1026). The scheduling decision may comprise radioresources (e.g., subchannels) assigned to the second station, amodulation and coding scheme selected for the second station, etc. Therelay station may resend the data to the second station based on thescheduling decision (block 1028).

FIG. 11 shows a design of an apparatus 1100 for supporting centralizedscheduling in multihop relay. Apparatus 1100 includes a module 1112 toreceive a first transmission (e.g., pilot) from a first station, amodule 1114 to estimate link quality for the first station based on thefirst transmission, a module 1116 to generate first CQI based on theestimated link quality for the first station, a module 1118 to send asecond transmission (e.g., pilot) to a second station, a module 1120 toreceive second CQI generated by the second station based on the secondtransmission, a module 1122 to send the first CQI and the second CQI tothe first station, a module 1124 to receive data sent by the firststation based on the first CQI, a module 1126 to receive a schedulingdecision determined a the base station based on the second CQI, and amodule 1128 to resend the data to the second station based on thescheduling decision.

The modules in FIGS. 9 and 11 may comprise processors, electronicsdevices, hardware devices, electronics components, logical circuits,memories, etc., or any combination thereof

FIGS. 8 through 11 show processes and apparatuses for a relay stationfor distributed and centralized scheduling in multihop relay. Processesand apparatuses for a base station and processes and apparatuses for asubscriber station may be implemented in an analogous manner based onFIGS. 6 and 7 and the description above.

In another aspect, the system may support distributed power controland/or centralized power control for uplink transmission with multihoprelay. Table 3 lists some characteristics of distributed and centralizedpower control.

TABLE 3 Power control Description Distributed Base station estimatesBS-RS link quality and sends power control power adjustment to relaystation. Relay station adjusts its transmit power based on the poweradjustment from the base station. Relay station estimates RS-SS linkquality and sends power adjustment to subscriber station. Subscriberstation adjusts its transmit power based on the power adjustment fromthe relay station. Centralized Base station obtains BS-RS and RS-SS linkqualities, power control generates first power adjustment for relaystation, and generates second power adjustment for subscriber station.Relay station adjusts its transmit power based on the first poweradjustment from the base station. Subscriber station adjusts itstransmit power based on the second power adjustment from the basestation.

In general, the quality of a given link may be estimated based on anytransmission received via that link. Since a relay station and asubscriber station may each transmit the CQICH periodically, an upstreamstation may use the CQICH to estimate the link quality for thetransmitting station. The following description assumes the use of theCQICH to estimate link quality.

A station (e.g., a subscriber station or a relay station) may transmitdata and/or control information (e.g., CQI) to an upstream station. Thetransmit power for data and the transmit power for control informationmay have a predetermined relationship, e.g., a fixed offset. The stationmay adjust its transmit power for both data and control informationbased on power adjustments received from the upstream station. Forexample, the transmit power may be (i) adjusted by an amount indicatedby a power adjustment, (ii) either increased or decreased by apredetermined amount as indicated by the power adjustment, or (iii)adjusted in some other manner based on the power adjustment. A poweradjustment may also be referred to as a power adjust, a power control(PC) command, a transmit power control (TPC) command, etc.

FIG. 12 shows a scheme for distributed power control for 2-hop relay.The first hop is from subscriber station 130 to relay station 120, andthe second hop is from relay station 120 to base station 110.

For the first hop, subscriber station 130 may transmit a first CQICH(which is denoted as CQICH #1) to relay station 120. Relay station 120may estimate the RS-SS link quality based on CQICH #1, generate a firstpower adjustment (which is denoted as power adjustment #1) based on theestimated RS-SS link quality, and send power adjustment #1 to subscriberstation 130. Subscriber station 130 may send data to relay station 120at transmit power determined based on power adjustment #1.

For the second hop, relay station 120 may transmit a second CQICH (whichis denoted as CQICH #2) to base station 110. Base station 110 mayestimate the BS-RS link quality based on CQICH #2, generate a secondpower adjustment (which is denoted as power adjustment #2) based on theestimated BS-RS link quality, and send power adjustment #2 to relaystation 120. Relay station 120 may resend the data received fromsubscriber station 130 to base station 110 at transmit power determinedbased on power adjustment #2.

FIG. 13 shows a scheme for centralized power control for 2-hop relay.Subscriber station 130 may transmit CQICH #1 to relay station 120, andrelay station 120 may estimate the RS-SS link quality based on CQICH #1.Relay station 120 may send CQICH #2 and the estimated RS-SS link qualityto base station 110. Base station 110 may generate power adjustment #1based on the estimated RS-SS link quality. Base station 110 may alsoestimate the BS-RS link quality based on CQICH #2 and generate poweradjustment #2 based on the estimated BS-RS link quality. Base station110 may send power adjustments #1 and #2 to relay station 120, which mayforward power adjustment #1 to subscriber station 130. Subscriberstation 130 may send data to relay station 120 at transmit powerdetermined based on power adjustment #1. Relay station 120 may resendthe data to base station 110 at transmit power determined based on poweradjustment #2.

FIGS. 12 and 13 show distributed and centralized power control,respectively, for 2-hop relay. Distributed and centralized power controlfor more than two hops may be performed in similar manner.

For N-hop distributed power control, a relay station may receive atransmission from the next downstream station, which may be a subscriberstation or another relay station. The relay station may estimate thelink quality for the next downstream station based on the receivedtransmission, generate a power adjustment based on the estimated linkquality, and send the power adjustment to the next downstream station.The relay station may receive data sent by the next downstream stationat transmit power determined based on the power adjustment from therelay station. The relay station may also send a transmission to thenext upstream station, which may be a base station or another relaystation. The relay station may receive a power adjustment generated bythe next upstream station based on link quality for the relay station,which may be estimated based on the transmission from the relay station.The relay station may resend the data received from the next downstreamstation to the next upstream station at transmit power determined basedon the power adjustment from the next upstream station.

For N-hop centralized power control, a relay station may receive atransmission from the next downstream station as well as estimated linkqualities for all further downstream stations, if any. The relay stationmay estimate the link quality for the next downstream station based onthe transmission from this downstream station. The relay station maysend a transmission as well as estimated link qualities for alldownstream stations to the next upstream station. The relay station mayreceive a power adjustment determined by a base station based on linkquality for the relay station, which may be estimated based on thetransmission from the relay station. The relay station may also receivepower adjustments for all downstream stations, which may be generated bythe base station based on the estimated link qualities for thesedownstream stations. The relay station may forward these poweradjustments to the next downstream station. The relay station mayreceive data sent by the next downstream station at transmit powerdetermined based on the power adjustment for this downstream station.The relay station may resend the data to the next upstream station attransmit power determined based on the power adjustment for the relaystation.

FIG. 14 shows a design of a process 1400 performed by a relay stationfor distributed power control in multihop relay, which may correspond toFIG. 12. The relay station may receive a first transmission from a firststation, which may be a subscriber station or another relay station(block 1412). The first transmission may comprise CQI sent on a CQICH,pilot, etc. The relay station may estimate link quality for the firststation based on the first transmission (block 1414), generate a firstpower adjustment based on the estimated link quality for the firststation (block 1416), and send the first power adjustment to the firststation (block 1418).

The relay station may send a second transmission to a second station,which may be a base station or another relay station (block 1420). Thesecond transmission may comprise CQI sent on a CQICH, pilot, etc. Therelay station may receive a second power adjustment generated by thesecond station based on the second transmission (block 1422). The relaystation may receive data sent by the first station at transmit powerdetermined based on the first power adjustment (block 1424). The relaystation may resend the data to the second station at transmit powerdetermined based on the second power adjustment (block 1426).

FIG. 15 shows a design of an apparatus 1500 for supporting distributedpower control in multihop relay. Apparatus 1500 includes a module 1512to receive a first transmission from a first station, a module 1514 toestimate link quality for the first station based on the firsttransmission, a module 1516 to generate a first power adjustment basedon the estimated link quality for the first station, a module 1518 tosend the first power adjustment to the first station, a module 1520 tosend a second transmission to a second station, a module 1522 to receivea second power adjustment generated by the second station based on thesecond transmission, a module 1524 to receive data sent by the firststation at transmit power determined based on the first poweradjustment, and a module 1526 to resend the data to the second stationat transmit power determined based on the second power adjustment.

FIG. 16 shows a design of a process 1600 performed by a relay stationfor centralized power control in multihop relay, which may correspond toFIG. 13. The relay station may receive a first transmission from a firststation, which may be a subscriber station or another relay station(block 1612). The first transmission may comprise CQI sent on a CQICH,pilot, etc. The relay station may estimate link quality for the firststation based on the first transmission (block 1614). The relay stationmay send the estimated link quality for the first station and a secondtransmission to a second station, which may be a base station or anotherrelay station (block 1616). The second transmission may comprise CQIsent on a CQICH, pilot, etc. The relay station may send the estimatedlink quality for the first station on the CQICH, on a feedback channel,in a MAC management message, or via some other means to the secondstation.

The relay station may receive first and second power adjustments fromthe second station, with the first power adjustment being generatedbased on the estimated link quality for the first station, and thesecond power adjustment being generated based on the second transmission(block 1618). The relay station may send the first power adjustment tothe first station (block 1620). The relay station may receive data sentby the first station at transmit power determined based on the firstpower adjustment (block 1622). The relay station may resend the data tothe second station at transmit power determined based on the secondpower adjustment (block 1624).

FIG. 17 shows a design of an apparatus 1700 for supporting centralizedpower control in multihop relay. Apparatus 1700 includes a module 1712to receive a first transmission from a first station, a module 1714 toestimate link quality for the first station based on the firsttransmission, a module 1716 to send the estimated link quality for thefirst station and a second transmission to a second station, a module1718 to receive first and second power adjustments from the secondstation, a module 1720 to send the first power adjustment to the firststation, a module 1722 to receive data sent by the first station attransmit power determined based on the first power adjustment, and amodule 1724 to resend the data to the second station at transmit powerdetermined based on the second power adjustment.

The modules in FIGS. 15 and 17 may comprise processors, electronicsdevices, hardware devices, electronics components, logical circuits,memories, etc., or any combination thereof

FIGS. 14 through 17 show processes and apparatuses for a relay stationfor distributed and centralized power control in multihop relay.Processes and apparatuses for a base station and processes andapparatuses for a subscriber station may be implemented in an analogousmanner based on FIGS. 12 and 13 and the description above.

FIG. 18 shows a block diagram of a design of base station 110, relaystation 120, and subscriber station 130 in FIG. 1. At base station 110,a transmit processor 1810 receives data for subscriber station 130 andother subscriber stations, processes (e.g., encodes, interleaves, andmodulates) the data, and generates data symbols. Transmit processor 1810also processes overhead information (e.g., MAP messages, poweradjustments, scheduling decisions, etc.) to obtain overhead symbols andprocesses pilot to obtain pilot symbols. Transmit processor 1810 furtherprocesses the data, overhead, and pilot symbols (e.g., for OFDM) andgenerates output chips. A transmitter (TMTR) 1812 conditions (e.g.,converts to analog, amplifies, filters, and frequency upconverts) theoutput chips and generates a downlink signal, which is transmitted viaan antenna 1814.

At relay station 120, an antenna 1834 receives the downlink signal frombase station 110 and provides a received signal to a receiver (RCVR)1836. Receiver 1836 conditions (e.g., filters, amplifies, frequencydownconverts, and digitizes) the received signal and provides samples. Areceive processor 1838 processes the samples (e.g., for OFDM) to obtainreceived symbols, processes received pilot symbols to obtain a channelestimate, and performs detection on received data and overhead symbolswith the channel estimate to obtain detected symbols. Receive processor1838 further processes (e.g., demodulates, deinterleaves, and decodes)the detected symbols to recover the data and overhead information sentby base station 110. A transmit processor 1830 processes the datareceived from base station 110, overhead information, and pilot togenerate data, overhead, and pilot symbols, respectively. Transmitprocessor 1830 further processes these symbols (e.g., for OFDM) togenerate output chips. A transmitter 1832 conditions the output chipsand generates a downlink relay signal, which is transmitted via antenna1834.

At subscriber station 130, the downlink relay signal from relay station120 is received by an antenna 1850, conditioned by a receiver 1852, andprocessed by a receive processor 1854 to recover the data resent byrelay station 120. The downlink signal from base station 110 is alsoreceived by antenna 1850, conditioned by receiver 1852, and processed byreceive processor 1854 to recover overhead information sent by basestation 110 in the transparent mode. Data, signaling (e.g., CQI), andpilot to send on the uplink are processed by a transmit processor 1856and conditioned by a transmitter 1858 to generate an uplink signal,which is transmitted via antenna 1850.

Relay station 120 receives and processes the uplink signal fromsubscriber station 130 to recover the data and signaling sent by thesubscriber station. Relay station 120 processes the data, signaling, andpilot to generate an uplink relay signal, which is transmitted to basestation 110. At base station 110, the uplink relay signal is received byantenna 1814, conditioned by a receiver 1816, and processed by a receiveprocessor 1818 to recover the data and signaling sent by relay station120.

Controllers/processors 1820, 1840 and 1860 direct the operation ofvarious units at base station 110, relay station 120, and subscriberstation 130, respectively. Controller/processor 1840 may perform ordirect process 800 in FIG. 8, process 1000 in FIG. 10, process 1400 inFIG. 14, process 1600 in FIG. 16 and/or other processes for thetechniques described herein. Memories 1822, 1842 and 1862 store data andprogram codes for base station 110, relay station 120, and subscriberstation 130, respectively.

The techniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware, firmware,software, or a combination thereof For a hardware implementation, theprocessing units used to perform the techniques may be implementedwithin one or more application specific integrated circuits (ASICs),digital signal processors (DSPs), digital signal processing devices(DSPDs), programmable logic devices (PLDs), field programmable gatearrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, a computer, or a combinationthereof.

For a firmware and/or software implementation, the techniques may beimplemented with code (e.g., procedures, functions, modules,instructions, etc.) that performs the functions described herein. Ingeneral, any computer/processor-readable medium tangibly embodyingfirmware and/or software code may be used in implementing the techniquesdescribed herein. For example, the firmware and/or software code may bestored in a memory (e.g., memory 1822, 1842 or 1862 in FIG. 18) andexecuted by a processor (e.g., processor 1820, 1840 or 1860). The memorymay be implemented within the processor or external to the processor.The firmware and/or software code may also be stored in acomputer/processor-readable medium such as random access memory (RAM),read-only memory (ROM), non-volatile random access memory (NVRAM),programmable read-only memory (PROM), electrically erasable PROM(EEPROM), FLASH memory, floppy disk, compact disc (CD), digitalversatile disc (DVD), magnetic or optical data storage device, etc. Thecode may be executable by one or more computers/processors and may causethe computer/processor(s) to perform certain aspects of thefunctionality described herein.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus for wireless communication,comprising: a processor; and a memory in electronic communication withthe processor, the memory embodying instructions, the instructions beingexecutable by the processor to: estimate link quality based on atransmission received from a first station; generate first channelquality information (CQI) based on the estimated link quality; send thefirst CQI to the first station; receive second CQI from a secondstation, the second CQI being different from the first CQI; receive datasent by the first station according to a first transmission scheduledetermined by the first station, the first transmission schedulecomprising an allocation of radio resources; identify a secondtransmission schedule for transmissions to the second station, thesecond transmission schedule comprising an allocation of radio resourcesto the second station; and send the data to the second station using theallocated radio resources based on the second transmission schedule. 2.The apparatus of claim 1, wherein the instructions are executable by theprocessor to: receive a pilot from the first station; estimate linkquality for the first station based on the pilot; and generate the firstCQI based on the estimated link quality for the first station.
 3. Theapparatus of claim 1, wherein the instructions are executable by theprocessor to: send a pilot to the second station; and receive the secondCQI generated by the second station based on the pilot.
 4. The apparatusof claim 1, wherein the first station schedules transmission of the datafrom the first station according to the first transmission schedule. 5.The apparatus of claim 4, wherein the at least one processor isconfigured to perform at least one of assigning radio resources to thesecond station and selecting a modulation and coding scheme for thesecond station to schedule transmission of the data to the secondstation.
 6. The apparatus of claim 1, wherein the instructions areexecutable by the processor to: schedule transmission of the data to thesecond station according to the second transmission schedule.
 7. Theapparatus of claim 1, wherein the first station is a base station andthe second station is a subscriber station.
 8. The apparatus of claim 1,wherein the instructions to identify the second transmission schedulecomprising an allocation of the radio resources to the second stationare executable by the processor to: analyze the second CQI; anddetermine the second transmission schedule comprising the allocation ofthe radio resources for the second station.
 9. The apparatus of claim 1,wherein the instructions to identify the second transmission schedulecomprising an allocation of the radio resources to the second stationare executable by the processor to: transmit the second CQI to the firststation; and receive the second transmission schedule comprising theallocation of the radio resources for the second station from the firststation.
 10. A method for wireless communication, comprising: estimatinglink quality based on a transmission received from a first station;generating first channel quality information (CQI) based on theestimated link quality; sending the first CQI to the first station;receiving second CQI from a second station, the second CQI beingdifferent from the first CQI; receiving data sent by the first stationaccording to a first transmission schedule determined by the firststation, the first transmission schedule comprising an allocation ofradio resources; identifying a second transmission schedule fortransmissions to the second station, the second transmission schedulecomprising an allocation of radio resources to the second station; andsending the data to the second station using the allocated radioresources based on the second transmission schedule.
 11. The method ofclaim 9, further comprising: receiving a first pilot from the firststation; and sending a second pilot to the second station, the first CQIbeing generated based on the first pilot and the second CQI beinggenerated based on the second pilot.
 12. The method of claim 9, furthercomprising: scheduling transmission of the data to the second stationaccording to the second transmission schedule.
 13. The method of claim9, wherein identifying the second transmission schedule comprising anallocation of the radio resources to the second station comprises:analyzing the second CQI; and determining the second transmissionschedule comprising the allocation of the radio resources for the secondstation.
 14. The method of claim 9, wherein identifying the secondtransmission schedule comprising an allocation of the radio resources tothe second station comprises: transmitting the second CQI to the firststation; and receiving the second transmission schedule comprising theallocation of the radio resources for the second station from the firststation.
 15. An apparatus for wireless communication, comprising: meansfor estimating link quality based on a transmission received from afirst station; means for generating first channel quality information(CQI) based on the estimated link quality; means for sending the firstCQI to the first station; means for receiving second CQI from a secondstation, the second CQI being different from the first CQI; means forreceiving data sent by the first station according to a firsttransmission schedule determined by the first station, the firsttransmission schedule comprising an allocation of radio resources; meansfor identifying a second transmission schedule for transmissions to thesecond station, the second transmission schedule comprising anallocation of radio resources to the second station; and means forsending the data to the second station using the allocated radioresources based on the second transmission schedule.
 16. The apparatusof claim 15, further comprising: means for receiving a first pilot fromthe first station; and means for sending a second pilot to the secondstation, the first CQI being generated based on the first pilot and thesecond CQI being generated based on the second pilot.
 17. The apparatusof claim 15, further comprising: means for scheduling transmission ofthe data to the second station according to the second transmissionschedule.
 18. A computer program product comprising a non-transitorycomputer-readable storage medium storing instructions executable by aprocessor to: estimate link quality based on a transmission receivedfrom a first station; generate first channel quality information (CQI)based on the estimated link quality; send the first CQI to the firststation; receive second CQI from a second station, the second CQI beingdifferent from the first CQI; receive data sent by the first stationaccording to a first transmission schedule determined by the firststation, the first transmission schedule comprising an allocation ofradio resources; identify a second transmission schedule fortransmissions to the second station, the second transmission schedulecomprising an allocation of radio resources to the second station; andsend the data to the second station using the allocated radio resourcesbased on the second transmission.
 19. The computer program product ofclaim 18, wherein the instructions are executable by the processor to:schedule transmission of the data to the second station according to thesecond transmission schedule.
 20. An apparatus for wirelesscommunication, comprising: a processor; a memory in electroniccommunication with the processor; and instructions stored in the memory,the instructions being executable by the processor to: send a pilot to arelay station; receive first channel quality information (CQI) generatedby the relay station based on the pilot; generate a first transmissionschedule comprising an allocation of radio resources to the relaystation; and send data to the relay station using the allocated radioresources, the data being sent by the relay station to a subscriberstation according to a second transmission schedule comprising anallocation of radio resources to the subscriber station.
 21. Anapparatus for wireless communication, comprising: a processor; a memoryin electronic communication with the processor; and instructions storedin the memory, the instructions being executable by the processor to:generate the first channel quality information (CQI) for a firststation; receive second CQI from a second station, the second CQI beingdifferent from the first CQI; send the first CQI and the second CQI tothe first station; receive data sent by the first station according to afirst transmission schedule determined by the first station, the firsttransmission schedule comprising an allocation of radio resources;receive a second transmission schedule from and determined by the firststation, the second transmission schedule identifying a radio resourceto allocate to the second station; and send the data to the secondstation based on the second transmission schedule.
 22. The apparatus ofclaim 21, wherein the instructions are executable by the processor to:receive pilot from the first station; estimate link quality for thefirst station based on the pilot; and generate the first CQI based onthe estimated link quality for the first station.
 23. The apparatus ofclaim 21, wherein the instructions are executable by the processor to:send pilot to the second station; and receive the second CQI generatedby the second station based on the pilot.
 24. The apparatus of claim 21,wherein the first station schedules transmission of the data from thefirst station according to the first transmission schedule, andgenerates the second transmission schedule.
 25. The apparatus of claim21, wherein the second transmission schedule comprises at least one ofradio resources assigned to the second station and a modulation andcoding scheme selected for the second station.
 26. The apparatus ofclaim 21, wherein the first station is a base station and the secondstation is a subscriber station.
 27. A method for wirelesscommunication, comprising: generating first channel quality information(CQI) for a first station; receiving second CQI from a second station,the second CQI being different from the first CQI; sending the first CQIand the second CQI to the first station; receiving data sent by thefirst station according to a first transmission schedule determined bythe first station, the first transmission schedule comprising anallocation of radio resources; receiving a second transmission schedulefrom and determined by the first station, the second transmissionschedule identifying a radio resource to allocate to the second station;and sending the data to the second station based on the secondtransmission schedule.
 28. The method of claim 27, further comprising:receiving a first pilot from the first station; and sending a secondpilot to the second station, the first CQI being generated based on thefirst pilot, and the second CQI being generated based on the secondpilot.
 29. The method of claim 27, wherein transmission of the data fromthe first station is scheduled by a base station according to the firsttransmission schedule, and the second transmission schedule is generatedby the base station.
 30. An apparatus for wireless communication,comprising: a processor; a memory in electronic communication with theprocessor; and instructions stored in the memory, the instructions beingexecutable by the processor to: send a pilot to a relay station; receivefirst channel quality information (CQI) and second CQI from the relaystation, the first CQI being generated based on the pilot, and thesecond CQI being sent by a subscriber station to the relay station, thesecond CQI being different from the first CQI; determine a transmissionschedule, the transmission schedule comprising an allocation of radioresources to allocate to the subscriber station; send data to the relaystation; and send the transmission schedule to the relay station, thedata being sent by the relay station to the subscriber station based onthe transmission schedule.